• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 215
  • 63
  • 60
  • 48
  • 35
  • 28
  • 7
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 558
  • 112
  • 109
  • 91
  • 88
  • 63
  • 61
  • 46
  • 45
  • 44
  • 42
  • 42
  • 40
  • 37
  • 36
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Conservação de energia em sistemas de iluminação pública e os seus efeitos na rede elétrica de distribuição /

Damato, Júlio Carlos. January 2005 (has links)
Resumo: O trabalho busca trazer uma contribuição na utilização da energia elétrica, através do melhor uso das lâmpadas de descarga à alta pressão, de vapor de mercúrio e de sódio. Dois aspectos são tratados: a influência deste tipo de lâmpada na qualidade de energia, uma vez que esta avaliação é difícil, por se tratar de uma carga distribuída por toda a cidade e o aspecto do dimensionamento dos condutores para os circuitos que têm uma alimentação exclusiva através de transformadores dedicados. A parte prática do trabalho está baseada em experimentos e medições feitas em uma subestação experimental montada no Laboratório de Alta Tensão na UNESP, campus de Guaratinguetá. Através de oscilografia, as formas de ondas de corrente e tensão, no lado de baixa tensão e média tensão, foram medidas, analisadas e avaliadas. Com a utilização de softwares gráficos foram comparadas as formas de ondas mostradas pelo equipamento com as curvas traçadas a partir de valores calculados. Foram avaliadas as influências dos transformadores de corrente e dos transformadores de potencial sobre as medições dos parâmetros elétricos de uma instalação. / Abstract: The work wants to give a contribution in the use of the electric power, trough the best use of the high pressure discharge lamps, of mercury and sodium. Two aspects are treated: the lamp type influence in Energy Quality, once this evaluation is difficult, for treating of a load distributed by the whole city, and the aspect of the dimensioning of the feeders for circuits that have and exclusive feeding through transformers.A brief revision of lighting concepts is made and also a study of harmonic current is presented. It was looked for, in research, to know the state of the art for the subject. The practical part of work is based on experiments and measurements made in a mounted experimental substation in UNESP High Tension Laboratory, campus of Guaratinguetá. Through oscilograph voltage and current waves formats, in low and high voltage sides, they were measured, analyzed and appraised. With utilization of graphics software was a made a comparison between the equipment oscilographed curves and curves acquire on calculated values. They were appraised the influences of voltage and current transformers about the measurents of the electric parameters of an installation. / Orientador: Oscar Armando Maldonado Astorga / Coorientador: José Luz Silveira / Banca: Agnelo Marotta Cassula / Banca: José Policarpo Gonçalves de Abreu / Mestre
282

Conservação de energia em sistemas de iluminação pública e os seus efeitos na rede elétrica de distribuição

Damato, Júlio Carlos [UNESP] 21 December 2005 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:29:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-21Bitstream added on 2014-06-13T18:59:49Z : No. of bitstreams: 1 damato_jc_me_guara.pdf: 907873 bytes, checksum: 1173d249b00c8dc682ed7ae9dce890c3 (MD5) / Universidade Estadual Paulista (UNESP) / O trabalho busca trazer uma contribuição na utilização da energia elétrica, através do melhor uso das lâmpadas de descarga à alta pressão, de vapor de mercúrio e de sódio. Dois aspectos são tratados: a influência deste tipo de lâmpada na qualidade de energia, uma vez que esta avaliação é difícil, por se tratar de uma carga distribuída por toda a cidade e o aspecto do dimensionamento dos condutores para os circuitos que têm uma alimentação exclusiva através de transformadores dedicados. A parte prática do trabalho está baseada em experimentos e medições feitas em uma subestação experimental montada no Laboratório de Alta Tensão na UNESP, campus de Guaratinguetá. Através de oscilografia, as formas de ondas de corrente e tensão, no lado de baixa tensão e média tensão, foram medidas, analisadas e avaliadas. Com a utilização de softwares gráficos foram comparadas as formas de ondas mostradas pelo equipamento com as curvas traçadas a partir de valores calculados. Foram avaliadas as influências dos transformadores de corrente e dos transformadores de potencial sobre as medições dos parâmetros elétricos de uma instalação. / The work wants to give a contribution in the use of the electric power, trough the best use of the high pressure discharge lamps, of mercury and sodium. Two aspects are treated: the lamp type influence in Energy Quality, once this evaluation is difficult, for treating of a load distributed by the whole city, and the aspect of the dimensioning of the feeders for circuits that have and exclusive feeding through transformers.A brief revision of lighting concepts is made and also a study of harmonic current is presented. It was looked for, in research, to know the state of the art for the subject. The practical part of work is based on experiments and measurements made in a mounted experimental substation in UNESP High Tension Laboratory, campus of Guaratinguetá. Through oscilograph voltage and current waves formats, in low and high voltage sides, they were measured, analyzed and appraised. With utilization of graphics software was a made a comparison between the equipment oscilographed curves and curves acquire on calculated values. They were appraised the influences of voltage and current transformers about the measurents of the electric parameters of an installation.
283

Real-time diffuse indirect illumination with virtual light meshes / Iluminação indireta difusa em tempo real usando malhas de luzes virtuais

Aquotte, Fabio de Almeida January 2017 (has links)
A iluminação indireta é capaz de elevar consideravelmente a qualidade visual de cenas renderizadas, mas é também uma operação custosa. Por este motivo, há muito esforço de pesquisa voltado para a renderização de iluminação indireta em tempo real. Apesar de atualmente existirem técnicas poderosas para a iluminação indireta em tempo real, elas fornecem ao artista apenas um controle grosseiro do equilíbrio entre qualidade e desempenho. Nós propomos uma Malha de Luzes Virtuais para calcular a iluminação indireta difusa numa cena, inspirados pelo uso de outras malhas auxiliares, como Malhas de Navegação e Malhas de Colisão. Uma Malha de Luzes Virtuais (MLV) é uma malha simplificada de luzes poligonais usadas para aproximar a luz refletida pela geometria real. Juntamente com a MLV, nós projetamos uma estrutura de dados de aceleração para atingir um desempenho eficiente com iluminação indireta usando uma MLV complexa. O uso da MLV apresenta algumas características vantajosas: maior controle artístico dos atributos da iluminação indireta; a possibilidade de integração com técnicas existentes como animação esquelética e geração procedural; e integração simples com ferramentas e processos de produção de arte existentes. Nossos resultados experimentais mostram que a iluminação indireta controlada por artistas é uma alternativa viável a métodos existentes. / Indirect illumination on a rendered scene can add a great deal to its visual quality, but it is also a costly operation. Therefore, a lot of research targets how to render indirect illumination in real-time. While powerful techniques for real-time indirect illumination currently exist, they provide only coarse-grained artistic control over the trade-off between quality and speed. We propose a Virtual Light Mesh to compute the scene’s diffuse indirect illumination, inspired by the use of other current auxiliary meshes such as Navigation Meshes and Collision Meshes. A Virtual Light Mesh (VLM) is a simplified mesh of polygonal lights used to approximate the light bounced by the real geometry. Together with the VLM, we design an acceleration data structure for efficient indirect illumination performance with a complex VLM. The use of VLM presents some positive properties: greater artistic control of the indirect illumination characteristics; the possibility of integration with existing techniques such as skeletal animation and procedural generation; and simple integration into existing asset production tools and pipelines. Our experimental results show that artist controlled indirect illumination is a viable alternative to existing methods.
284

A System for In Situ UV-Visible Illumination of Transmission Electron Microscope Samples

January 2012 (has links)
abstract: A system for illuminating a sample in situ with visible and UV light inside a transmission electron microscope was devised to study photocatalysts. There are many factors which must be considered when designing and building such a system. These include both mechanical, optical, and electron optical considerations. Some of the restrictions posed by the electron microscope column are significant, and care must be taken not to degrade the microscope's electron optical performance, or to unduly restrict the other current capabilities of the microscope. The nature of these various design considerations is discussed in detail. A description of the system that has been added to the microscope at ASU, an FEI Tecnai F20 environmental transmission electron microscope is also given. The system includes a high brightness broadband light source with optical filters, a fiber to guide the light to the sample, and a system for precisely aligning the fiber tip. The spatial distribution and spectrum of the light reaching the sample has been characterized, and is described in detail. / Dissertation/Thesis / M.S. Materials Science and Engineering 2012
285

Post processing Treatment of InGaZnO Thin Film Transistors for Improved Bias-Illumination Stress Reliability

January 2013 (has links)
abstract: This thesis work mainly examined the stability and reliability issues of amorphous Indium Gallium Zinc Oxide (a-IGZO) thin film transistors under bias-illumination stress. Amorphous hydrogenated silicon has been the dominating material used in thin film transistors as a channel layer. However with the advent of modern high performance display technologies, it is required to have devices with better current carrying capability and better reproducibility. This brings the idea of new material for channel layer of these devices. Researchers have tried poly silicon materials, organic materials and amorphous mixed oxide materials as a replacement to conventional amorphous silicon layer. Due to its low price and easy manufacturing process, amorphous mixed oxide thin film transistors have become a viable option to replace the conventional ones in order to achieve high performance display circuits. But with new materials emerging, comes the challenge of reliability and stability issues associated with it. Performance measurement under bias stress and bias-illumination stress have been reported previously. This work proposes novel post processing low temperature long time annealing in optimum ambient in order to annihilate or reduce the defects and vacancies associated with amorphous material which lead to the instability or even the failure of the devices. Thin film transistors of a-IGZO has been tested for standalone illumination stress and bias-illumination stress before and after annealing. HP 4155B semiconductor parameter analyzer has been used to stress the devices and measure the output characteristics and transfer characteristics of the devices. Extra attention has been given about the effect of forming gas annealing on a-IGZO thin film. a-IGZO thin film deposited on silicon substrate has been tested for resistivity, mobility and carrier concentration before and after annealing in various ambient. Elastic Recoil Detection has been performed on the films to measure the amount of hydrogen atoms present in the film. Moreover, the circuit parameters of the thin film transistors has been extracted to verify the physical phenomenon responsible for the instability and failure of the devices. Parameters like channel resistance, carrier mobility, power factor has been extracted and variation of these parameters has been observed before and after the stress. / Dissertation/Thesis / M.S. Electrical Engineering 2013
286

Illumination for Real-Time Rendering of Large Architectural Environments

Fahlén, Markus January 2006 (has links)
This thesis explores efficient techniques for high quality real-time rendering of large architectural environments using affordable graphics hardware, as applied to illumination, including window reflections, shadows, and "bump mapping". For each of these fields, the thesis investigates existing methods and intends to provide adequate solutions. The focus lies on the use of new features found in current graphics hardware, making use of new OpenGL extensions and functionality found in Shader Model 3.0 vertex and pixel shaders and the OpenGL 2.0 core. The thesis strives to achieve maximum image quality, while maintaining acceptable performance at an affordable cost. The thesis shows the feasibility of using deferred shading on current hardware and applies high dynamic range rendering with the intent to increase realism. Furthermore, the thesis explains how to use environment mapping to simulate true planar reflections as well as incorporates relevant image post-processing effects. Finally, a shadow mapping solution is provided for the future integration of dynamic geometry.
287

Liturgia cinematografica : luzes e sombras nazistas / Cinematographic liturgy: nazist lights and shades

Silva, Josirley Maria Menezes da, 1977- 23 February 2006 (has links)
Orientador: Milton Jose de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação / Made available in DSpace on 2018-08-08T12:43:23Z (GMT). No. of bitstreams: 1 Silva_JosirleyMariaMenezesda_M.pdf: 29768864 bytes, checksum: 2dcb63f4e7a5cd98841db0e021aeae79 (MD5) Previous issue date: 2006 / Resumo: Nesta dissertação apresentam-se interpretações para a Luz cinematográfica: políticas e manipulações dos momentos em luz no cinema. E suas sombras: as inscrições guardadas nos espaços escuros da tela: interpretações e significados. Essas interpretações dão-se em torno do filme "O triunfo da vontade", de Leni Riefenstahl, lugar em que se coloca o olhar, buscando, nas transparências e opacidades da imagem, remontar os vitrais que constituem as imagens nazistas e seus valores de ordem, pureza, poder e sacralização: uma transparência controlada em luz e difusa em sombras; sugerida nas sombras e opacas na luz. Através de um caminho - os dias e os lugares em que acontece o Congresso Nazista - procuram-se as imagens latentes em construção. / Abstract: I explored interpretations for the "light" as it appears in the movies: politics and manipulations of light moments, and its shadows: interpretations and meannings. These interpretations are presented in a major production: "The triumph of will", by Leni Riefenstahl, as a counterface of Dürer's stained glasses in Nürenberg: images of order, purety, power and religious values: a ligth control and uncontrol shadows: during the Nazi Congress, 1934. / Mestrado / Educação, Conhecimento, Linguagem e Arte / Mestre em Educação
288

Conforto térmico e iluminação natural no edifício administrativo da Escola de Engenharia de São Carlos: o bloco E1 / Architecture, thermal comfort and natural illumination in the administrative building of the School of Engineering of São Carlos / USP: the E1 block

Cíntia Cristina Vieira 06 August 2008 (has links)
A presente pesquisa consiste em uma análise do edifício administrativo da Escola de Engenharia de São Carlos pertencente à Universidade de São Paulo, do ponto de vista de conforto térmico e iluminação natural. O processo de investigação se dá em algumas etapas: análise projetual enfatizando os aspectos relativos ao conforto ambiental (microclima, partidos arquitetônicos, implantação, materiais, técnicas construtivas, aberturas, envidraçamentos, diagramas e esquemas de estudo); aplicação de questionários aos usuários; e medições in loco de níveis de iluminação e de variáveis ambientais de conforto térmico. Os resultados foram analisados e comparados, para que a partir destes seja possível obter uma avaliação das soluções e técnicas empregadas quanto às questões de térmica e iluminação, contribuindo assim no aperfeiçoamento de técnicas projetuais. Objetiva-se com estas técnicas a obtenção de conforto ambiental e redução no consumo de energia, para edifícios do padrão do estudado, o qual é visto repetir-se incalculavelmente em edifícios administrativos, de escritórios e escolares. / This research is an analysis of the administrative building of the Escola de Engenharia de São Carlos belonging to the Universidade de Sao Paulo, from the point of view of thermal comfort and natural illumination. The process of investigation takes place in some steps: architectural design analysis emphasizing aspects related to environmental comfort (microclimate, architectural parties, implantation, materials, constructive techniques, openings, glassing, diagrams, and study schemes); application of questionnaires to users, and on-site measurements of environmental variables of thermal comfort and levels of illumination. The results were analyzed and compared, so that from the results it\'s possible to evaluate the solutions and applied techniques related to thermal and illumination aspects, thus contributing in the development of design techniques. The objective with these techniques is obtaining environmental comfort and reduction in energy consumption in buildings with the same pattern of use, which is seen to be repeated a lot of times in buildings for administrative use, offices and schools.
289

[en] SHADOW OF ILLUMINATION: AN ICONOLOGICAL ANALYSIS OF ILLEGIBILITY / [pt] SOMBRA DA ILUMINURA: UMA ANÁLISE ICONOLÓGICA DA ILEGIBILIDADE

MARCUS VINICIUS DE PAULA 17 June 2008 (has links)
[pt] Este trabalho utiliza o método iconológico de análise desenvolvido por W.J.T. Mitchell para expandir a noção de iluminura e dissolver a oposição entre legível e ilegível. Na primeira parte desta tese são analisados e definidos os mecanismos de leitura da iluminura e suas relações com as convenções da legibilidade e da ilegibilidade. Na segunda parte aborda-se essa mesma questão por meio de outra perspectiva, que envolve as transformações gráficas sofridas pelas páginas dos jornais a partir da virada do século XIX para o século XX. / [en] This work uses the iconological method of analysis developed by W.J.T. Mitchell to expand on the notion of illlumination and to break up the antagonism between the legibel and the illegible.In the first part of this thesis the mechanisms of reading illumination and their relation with the conventions of legibility and illegibility are analized and defined. In the second part, this same subject is approached from another perspective wich has envolved with the graphic transformation of newspaper pages at the end of the 19th Century end the beginning of the 20th Century.
290

Ambient Occlusion for Dynamic Objects and Procedural Environments

Jansson, Joel January 2013 (has links)
In computer graphics, lighting is an important area. To simulate shadows from area light sources, indirect lighting and shadows from indirect light, a class of algorithms commonly known as global illumination algorithms can be used. Ambient occlusion is an approximation to global illumination that can emulate shadows from area light sources and shadows from indirect light, giving very soft shadows. For real-time applications, ambient occlusion can be precomputed and stored in maps or per vertex. However, that can only be done with good results if the geometry is static. Therefore, a number of methods that can handle more or less dynamic scenes have been introduced in the recent years. In this thesis, a collection of ambient occlusion methods for dynamic objects and procedural environments will be described. The main contribution is the introduction of a novel method that handles ambient occlusion for procedural environments. Another contribution is a description of an implementation of Screen Space Ambient Occlusion (SSAO). SSAO is an algorithm that calculates approximate ambient occlusion in real-time by using the depths of surrounding pixels. It handles completely dynamic scenes with good performance. The method for procedural environments handles the scenario where a number of building blocks are procedurally assembled at run-time. The idea is to precompute an ambient occlusion map for each building block where the self-occlusion is stored. In addition, an ambient occlusion grid is precomputed for each block to accommodate the inter-block occlusion. At run-time, after the building blocks have been assembled, the ambient occlusion from the grids is blended with the ambient occlusion from the maps to generate new maps, valid for the procedural environment. Following that, the environment can be rendered with high quality ambient occlusion at almost no cost, in the same fashion as for a static environment where the ambient occlusion maps can be completely precomputed.

Page generated in 0.0916 seconds